DTC P0122 Throttle Position (TP) Sensor Circuit Low Voltage. Chevrolet PJJ 2000

For 1990-2009 cars
Engine Controls Components
Engine Data Sensors
OBD II Symbol Description Notice
Powertrain Control Module Connector End Views
Handling ESD Sensitive Parts Notice

### Circuit Description

The PCM supplies a 5.0 V reference signal and a ground to the sensor. The TP sensor sends a voltage signal back to the PCM relative to the throttle plate opening. The voltage will vary from approximately 0.35 V at closed throttle, to over 4.65 V at wide open throttle.

### Conditions For Running The DTC

The engine is running.

### Conditions For Setting The DTC

The TP sensor reads less than 0.20 volts for 15 seconds.

### Action Taken When the DTC Sets

• | The Malfunction Indicator Lamp (MIL) will illuminate after two consecutive ignition cycles in which the diagnostic runs with the fault active.

• | The PCM will record the operating conditions at the time that the diagnostic fails. This information will store in the Freeze Frame and Failure Records buffers.

• | A history DTC stores.

• | The coolant fan turns ON.

• | The TP angle will default to 0 percent when the vehicle speed is less than 3 km/h (2 mph) and 10 percent when the vehicle speed is greater than 3 km/h (2 mph) (The scan tool will display the defaulted value).

### Conditions for Clearing the MIL/DTC

• | The MIL will turn OFF after three consecutive ignition cycles in which the diagnostic runs without a fault.

• | A history DTC will clear after 40 consecutive warm up cycles without a fault.

• | Use a scan tool to clear the DTCs.

### Diagnostic Aids

If a DTC P0122 cannot be duplicated, the information included in the Freeze Frame data can be useful. Use the scan tool DTC information data in order to determine the status of the DTC. If the DTC occurs intermittently, use the DTC P0105 Diagnostic table in order to help isolate the problem.

### Test Description

The numbers below refer to the step numbers on the diagnostic table.

1. The TP sensor has an auto zeroing feature. If the voltage reading is between 0.20 Volts and 0.90 Volts, the PCM will automatically assume this as a closed throttle position (0 percent).

2. This simulates a DTC P0123. If the PCM recognizes the high voltage signal, this indicates that the PCM and the wiring are OK.

3. This simulates a high voltage signal which will identify an open in the signal circuit.

4. Important: The Powertrain Control Module (PCM) uses a single internal 5.0 volt power supply to supply power to all the engine control components. If one component shorts its 5.0 volt reference circuit to ground or battery voltage, the other 5.0 volt reference circuits will also have a low or high voltage.

   If any additional DTCs are set, check the 5.0 Volt reference circuits for a short to ground.

5. If the test lamp illuminates while probing the TP signal circuit terminal in step 5, then the TP signal circuit is shorted to ground.

6. Reprogram the replacement PCM and perform the Crankshaft Position System Variation Learn procedure.

#### DTC P0122-Throttle Position (TP) Sensor Circuit Low Voltage

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform the Powertrain On Board Diagnostic (OBD) System Check? | -- | Go to Step 2 | Go to Powertrain On Board Diagnostic (OBD) System Check

2

1. Turn ON the ignition, with the engine OFF.
2. Install a scan tool.

Does the TP sensor voltage measure below the specified value?

0.2 V

Go to Step 4

Go to Step 3

3

1. Review the Freeze Frame data and record the parameters.
2. Start the engine.
3. Operate the vehicle within the Freeze Frame conditions and Conditions For Running the DTC as specified.

Does the TP sensor voltage measure below the specified value?

0.2 V

Go to Step 4

Go to Step 12

4

1. Turn OFF the ignition.
2. Disconnect the TP sensor connector.
3. Connect a fused jumper wire between the following circuits at the connector.

• | 5.0 Volt reference circuit

• | TP sensor signal circuit

4. Turn ON the ignition, with the engine OFF.

Does the TP sensor voltage measure greater than the specified value?

4.0 V

Go to Step 10

Go to Step 5

5

1. Remove the fuse jumper wire.
2. Connect a test lamp between the following circuits at the TP sensor connector.

• | Battery positive

• | TP sensor signal circuit

Does the TP sensor voltage measure greater than the specified value?

4.0 V

Go to Step 6

Go to Step 8

6

Important:: The Powertrain Control Module (PCM) uses a single internal 5.0 volt power supply to supply power to all the engine control components. If one component shorts its 5.0 volt reference circuit to ground or battery voltage, the other 5.0 volt reference circuits will also have a low or high voltage.

1. Turn OFF the ignition.
2. Test for the following conditions in the 5.0 V reference:

• | Open circuit

• | Short to ground

3. If a problem is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 12

Go to Step 7

7

1. Inspect the 5.0 V reference circuit for a poor connection at the PCM.
2. If a problem is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 12

Go to Step 11

8

1. Turn OFF the ignition.
2. Test for the following conditions in the TP sensor signal circuit:

• | Open circuit

• | Short to ground

3. If a problem is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 12

Go to Step 9

9

1. Inspect the TP sensor signal circuit for a poor connection at the PCM.
2. If a problem is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 12

Go to Step 11

10

1. Turn OFF the ignition.
2. Inspect the TP sensor connector for a poor connection.
3. If the TP sensor connector is OK, replace the TP sensor. Refer to the Throttle Position Sensor Replacement .

Did you complete the replacement?

--

Go to Step 12

--

11 | Important:: The replacement PCM must be programmed and the Crankshaft Position Variation procedure must be performed. Refer to Powertrain Control Module Replacement/Programming and Crankshaft Position System Variation Learn . Replace the PCM. Did you complete the replacement? | -- | Go to Step 12 | --

12

1. Use a scan tool to clear the DTCs.
2. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

--

Go to Step 2

System OK